We enumerate all the principal congruence link complements in $S^3$, there by answering a question of W. Thurston. Related articles: Technical Report: All Principal Congruence Link Groups (arXiv:1902.04722), All Known Principal Congruence Links (arXiv:1902.04426).
This is a technical report accompanying the paper All Principal Congruence Link Groups (arXiv:1802.01275) classifying all principal congruence link complements in S^3 by the same authors. It provides a complete overview of all cases (d,I) that had to be considered, as well as describes the necessary computations and computer programs written for the classification result.
This report lists the link diagrams in S^3 for all principal congruence link complements for which such a link diagram is known. Several unpublished link diagrams are included. Related to this, we also include one link diagram for an arithmetic regular tessellation link complement.
For an arbitrary positive integer $n$ and a pair $(p, q)$ of coprime integers, consider $n$ copies of a torus $(p,q)$ knot placed parallel to each other on the surface of the corresponding auxiliary torus: we call this assembly a torus $n$-link. We compute economical presentations of knot groups for torus links using the groupoid version of the Seifert--van Kampen theorem. Moreover, the result for an individual torus $n$-link is generalized to the case of multiple nested torus links, where we inductively include a torus link in the interior (or the exterior) of the auxiliary torus corresponding to the previous link. The results presented here have been useful in the physics context of classifying moduli space geometries of four-dimensional ${mathcal N}=2$ superconformal field theories.
Let $Gamma_g$ denote the orientation-preserving Mapping Class Group of the genus $ggeq 1$ closed orientable surface. In this paper we show that for fixed $g$, every finite group occurs as a quotient of a finite index subgroup of $Gamma_g$.
We prove the vanishing of certain low degree cohomologies of some induced representations. As an application, we determine certain low degree cohomologies of congruence groups.